The present invention relates to injection molding machines and relates, in particular, to machines having a plurality of axially arranged mold stations each station having cooperating mold plates defining mold cavities in well known fashion. This mold arrangement is known in the art as a stack mold.
In prior art machines a plurality of sets of mold plates, one set of mold plates for each mold station, are operated, open and closed, by a variety of mechanisms many of which are complicated and obstruct access for servicing molds at the various mold stations. Typical prior art mold operating mechanisms are shown in FIG. 2 of U.S. Pat. No. 3,659,997 and FIG. 1 of U.S. Pat. No. 4,207,051.
In prior art arrangements there are numerous problems relating to alignment, support and precise movement of mold plates in order to achieve the highest quality molded product with minimum wear and tear of the mechanisms utilized to open and close the mold cavity at the various mold stations.
One other problem is the lack of adequate access in the open mold condition to service the molds and mold plates and to replace molds without having to dismantle the molding machine.
That is, many prior art units support the mold plates on the machine tie rods which involves a cumbersome, time consuming, laborious task when one wishes to replace molds. Such a step frequently involves removal of tie rods.
Furthermore, it is desirable to provide a mold actuating mechanism that moves the various sets of mold plates from the open and closed positions so that all mold stations open and close simultaneously and precisely during the course of a continuous molding cycle.
In addition it is desirable to provide a mechanism that one can "overstroke" readily to increase access to service and replace molds and/or mold plates without major disassembly of the molding machine.
The term overstroke is intended to mean intentional opening of the various mold stations a distance beyond the normal open stroke distance of the normal cycle of operation.
A set of mold plates in the disclosed embodiment of the present invention includes mold plates, per se, and support plates to which the mold plates are attached, sometimes referred to collectively as a "set of plates".